In a hydrogen production process that is currently employed, industrially, a hydrocarbon or the like is reformed through steam reforming or partial oxidation to a gas containing hydrogen and carbon monoxide as major components, and then carbon monoxide is reacted with steam according to the following chemical reaction formula, thereby producing hydrogens.CO+H2O→CO2+H2 
The gas thus produced contains a large amount of CO2 along with hydrogen, and CO2 is necessarily removed and recovered for industrial utilization of hydrogen.
As a removing and recovering technique of CO2, a chemical absorption method, such as an amine absorption method, a physical adsorption method, such as PSA (pressure swing adsorption), and the like are currently employed. However, these CO2 removing and recovering techniques consume a large amount of energy for a regeneration process of the absorbent or the adsorbent, and the cost therefor occupies a half or more of the cost for separation of CO2.
In contrast, membrane separation may be operated continuously and does not require a regeneration process of the absorbent or the adsorbent, and therefore membrane separation is expected as an energy saving process.
Patent Literatures 1 and 2 describe the use of an organic polymer membrane functioning under a wet condition as a CO2 facilitated transport membrane.
FIG. 5 is a flow chart showing a hydrogen production Process by separating and recovering CO2 by utilizing membrane separation with the organic polymer membrane described in Patent Literatures 1 and 2.
A hydrocarbon or an alcohol as a raw material is reformed in a steam reformer (10) to form H2, CO2, CO, CH4 (small amount) and H2O, which are then introduced to a water gas shift reactor (11), in which CO in the gas is shifted to CO2, thereby decreasing the amount of CO in the gas. The gas thus formed is fed to a separation module (12), in which CO2 is separated and recovered with an organic polymer membrane (13), thereby resulting in an H2 concentrated gas.
As described above, CO2 may be recovered highly selectively by using an organic polymer membrane as a separation membrane with a CO2/H2 separation selectivity of 10 or more.
On the other hand, the separation membrane has a small CO2 permeability of approximately 2×10−7 (mol/(m2·s·Pa)) at most, but in consideration of application to a large-scale hydrogen production plant, the CO2 permeability is desirably 5×10−7 (mol/(m2·s·Pa)) or more, and the CO2/H2 separation. selectivity is desirably 10 or more.
Nonpatent Literature 1 reports results of CO2/H2 separation using a hydrophobic zeolite membrane, in which hydrogen having a small molecular size preferentially permeates under a dry condition, and under a wet condition, CO2 permeates with slight priority, but the CO2/H2 separation selectivity is as small as from 2.9 to 6.2.    Patent Literature 1: JP-A-2008-36463    Patent Literature 2: Japanese Patent No. 4,264,194    Nonpatent Literature 1: Journal. of Membrane Science (2010), vol. 360, pp. 284-291